In recent years, reductions in weight and thickness of each of a display apparatus such as a flat panel display (FPD: a liquid crystal display apparatus or an organic EL display apparatus, for example) and a solar cell have been advanced through development of a visual communication technology. A glass substrate has hitherto been used as a substrate for use in each of the display apparatus and the solar cell in many cases. The glass substrate is excellent in transparency, solvent resistance, gas barrier property, and heat resistance. However, when one attempts to reduce the thickness of glass for forming the glass substrate, the glass substrate is reduced in weight and simultaneously exhibits excellent flexibility, but there arises a problem in that the glass substrate becomes difficult to handle because of its insufficient impact resistance.
In order to improve handling property of a thin glass substrate, there have been proposed a flexible substrate obtained by applying a resin solution onto a glass surface, followed by drying (see, for example, Patent Documents 1 and 2) and a flexible substrate including a resin film attached to a glass surface (see, for example, Patent Literature 3). However, even in the case of using any of those technologies, a flexible substrate satisfying sufficient impact resistance in a manufacturing step of a display device which requires high reliability under high temperature and high humidity has not been obtained yet.
Further, the flexible substrate obtained by applying a resin solution onto a glass surface, followed by drying, has a problem in that the resin solution foams during the applying step and the drying step, resulting in deterioration in external appearance. Meanwhile, the flexible substrate including a resin film attached to a glass surface has a problem in that a stress, which is necessary for enhancing impact resistance of glass, is not sufficiently applied to glass, and hence sufficient impact resistance cannot be obtained. In addition, when a resin solution or a solvent is used as an adhesive for attaching the resin film, a wrinkle is liable to occur in the film. The wrinkle in the film not only causes a problem in an external appearance of a flexible substrate but also causes a problem in that the film ruptures when a measure for preventing the occurrence of the wrinkle is taken.